Ocular surface squamous neoplasia (OSSN), the most common ocular surface tumor, manifests as an abnormal growth of squamous epithelial cells on the eye’s surface. OSSN can be either benign or malignant.

In the US, OSSN occurs between 0.34 and 8.45 times per million people per year, and in Australia up to 19 times per million people per year.

The incidence of OSSN is higher in areas closer to the equator. OSSN is spread more in fair-skinned older people. The average age of patients with OSSN is 56 years.

What Factors Predispose OSSN?

Ultraviolet (UV) radiation is why OSSN is more common in fair-skinned people and closer to the equator. UV radiation can cause mutations in the p53 tumor suppressor gene, which increases the chance of uncontrolled cell division. Mutations in p53 have been found in some patients with OSSN.

Human papillomavirus (HPV) increases the risk of OSSN. HPV can change the p53 gene. HPV is associated with benign lesions of the conjunctival epithelium, as well as with malignant neoplasms.

According to South African scientists, human immunodeficiency virus or acquired immunodeficiency syndrome occurs in 79% of patients with OSSN. OSSN can serve as a marker for undetected HIV.

Lifestyle factors. Smoking, damage to the ocular surface, chemicals (petroleum, beryllium, trifluridine, arsenic), and vitamin A deficiency predispose to OSSN.

Treatment of OSSN

In the past, the primary treatment for OSSN was surgical excision of the tumor. However, the probability of recurrence after surgery reached 56%.

Over the past 20 years, alternative and additional treatment methods have appeared. Mitomycin C (MMC), 5-fluorouracil, and interferon-alpha-2b (IFN) are used to treat OSSN. These drugs are administered topically as monotherapy or as an adjunct to surgical excision if there is an increased risk of recurrence. The use of a topical preparation as primary therapy avoids surgical complications.

Treatment of OSSN with Interferon-Alpha-2b

Interferons are signaling molecules produced by immune cells to fight viruses, tumors, and pathogens.

Most physicians treat OSSN with mitomycin C or interferon-alpha-2b. MMS can cause side effects such as eye pain, tearing, irritation, and limbal stem cell deficiency. Compared to mitomycin C, interferon is safer and causes fewer side effects.

In an Indian clinical study, patients with OSSN were administered 1 million IU/mL IFN-alpha-2b eye drops 4 times daily until complete clinical resolution of the tumor. Patients were followed monthly until tumor regression, then every 3 months for 1 year, and every 6 months. In 22 of 24 patients (91.6%), the tumors wholly resolved within 3.25 months. At the end of the follow-up period, no long-term complications or relapses were found in the patients.

Two patients (8.3%) did not respond to topical IFN-alpha-2b and were subsequently treated surgically. These patients were diagnosed with squamous cell carcinoma.

Side effects:

  • One patient (4.2%) had conjunctival hyperemia with foreign body sensation.
  • One patient (4.2%) developed spontaneous intra-tumor bleeding after 3 weeks of topical administration of IFN-alpha-2b in a papillomatous tumor on the leg. Possibly, a reduction in the size of the tumor increased its mobility, which led to mechanical injury and bleeding.

Interferon Can Be Used Without A Refrigerator

It is vital to store interferon preparations in the refrigerator at 2-8°C. However, cold storage is not always possible due to the lack of a fridge.

Indian scientists studied the efficacy and safety of interferon-alpha-2b eye drops without cooling as a therapy for immunodeficiency and/or treatment of squamous cell neoplasia of the ocular surface.

31 OSSN patients received IFN-alpha-2b eye drops at a dose of 1 million IU/mL 4 times a day during treatment and thereafter for at least 1 month after complete clinical resolution of the tumor. After a three-month follow-up, 26 (83.9%) tumors completely resolved. Four (12.9%) tumors partially resolved, and one (3.2%) tumor did not respond to treatment and was later surgically removed. The average time for complete resolution of the tumor is 12 weeks. Relapse was noted in one case (3.8%) after 6 weeks of a complete solution.

There were no significant differences between treatment outcomes in this study and studies that used chilled interferon. The probable reason is the interferon’s stability at room temperature, close to body temperature, or the artificial tear compound, which is part of the eye drops and makes them thermally stable.

Findings

Interferon-alpha-2b drops are the least invasive treatment for ocular surface squamous cell neoplasia and are a safe alternative to radiotherapy, topical mitomycin C, intralesional injection of IFN-alpha-2b, and surgical excision.

It is crucial to store interferon preparations in the refrigerator at 2-8°C. However, an Indian study has shown that recombinant interferon-alpha-2b eye drops without refrigeration for the treatment of OSSN are equally effective and safe.

If the stability of interferons over a wide range of temperatures is substantiated and confirmed by further studies, this can reduce the cost of refrigeration equipment for storage and transportation and, as a result, reduce the cost of treatment.

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